This invention relates to an ink composition for forming a thin metal oxide film on a glass substrate.
It is known to form a thin metal oxide film on a substrate with an ink containing a base metal compound such as metal oxide hydrate or a metal alkoxide, a binder such as a resin, a solvent and other additives such as a pigment and the like.
For example, JP-A-63-48372 discloses an ink composition containing an organic coloring material, a binder such as a silicon alkoxide, and a solvent such as an alkyl alcohol.
JP-A-64-56776 discloses a heat-resistant ink for an ink jet printer. This ink contains a hydrolyzed metal alkoxide in the form of solid, a solvent, a binder and an electric conductivity imparting agent.
JP-A-2-60974 discloses an ink composition containing a compound containing a base metal such as a metal alkoxide, abietic acid as a viscosity-increasing agent, and a solvent such as butyl carbitol.
It is known to form a thin film on a substrate by screen printing, gravure, intaglio printing, stamping or spraying. For example, U.S. Pat. No. 5,108,479 discloses a method for forming a functional film on a glass plate by screen printing with an ink composition containing a metal alkoxide and a viscosity-increasing agent such as ethyl cellulose or nitrocellulose.
However, as is mentioned hereinabove, when a metal alkoxide is contained in an ink composition, it is necessary to hydrolyze the metal alkoxide to form a sol through polycondensation. With this, viscosity of the ink tends to change and its pot life tends to be shortened. When a conventional cellulose type viscosity-increasing agent is contained in an ink, a large amount of carbon tends to remain in a thin film even after drying and baking of the thin film. Therefore, the thin film tends to have a yellowish brown color damaging its external appearance. Furthermore, its strength such as scratch resistance tends to be substantially lowered.